// SPDX-License-Identifier: GPL-2.0
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/irq.h>
#include <linux/smp.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/cpu.h>
#include <linux/of.h>
#include <linux/spinlock.h>
#include <linux/msi.h>

#include <asm/smp.h>
#include <asm/machdep.h>
#include <asm/irq.h>
#include <asm/errno.h>
#include <asm/xics.h>
#include <asm/rtas.h>

/* RTAS service tokens */
static int ibm_get_xive;
static int ibm_set_xive;
static int ibm_int_on;
static int ibm_int_off;

static void ics_rtas_unmask_irq(struct irq_data *d)
{
        unsigned int hw_irq = (unsigned int)irqd_to_hwirq(d);
        int call_status;
        int server;

        pr_devel("xics: unmask virq %d [hw 0x%x]\n", d->irq, hw_irq);

        if (hw_irq == XICS_IPI || hw_irq == XICS_IRQ_SPURIOUS)
                return;

        server = xics_get_irq_server(d->irq, irq_data_get_affinity_mask(d), 0);

        call_status = rtas_call(ibm_set_xive, 3, 1, NULL, hw_irq, server,
                                DEFAULT_PRIORITY);
        if (call_status != 0) {
                printk(KERN_ERR
                        "%s: ibm_set_xive irq %u server %x returned %d\n",
                        __func__, hw_irq, server, call_status);
                return;
        }

        /* Now unmask the interrupt (often a no-op) */
        call_status = rtas_call(ibm_int_on, 1, 1, NULL, hw_irq);
        if (call_status != 0) {
                printk(KERN_ERR "%s: ibm_int_on irq=%u returned %d\n",
                        __func__, hw_irq, call_status);
                return;
        }
}

static unsigned int ics_rtas_startup(struct irq_data *d)
{
        /* unmask it */
        ics_rtas_unmask_irq(d);
        return 0;
}

static void ics_rtas_mask_real_irq(unsigned int hw_irq)
{
        int call_status;

        if (hw_irq == XICS_IPI)
                return;

        call_status = rtas_call(ibm_int_off, 1, 1, NULL, hw_irq);
        if (call_status != 0) {
                printk(KERN_ERR "%s: ibm_int_off irq=%u returned %d\n",
                        __func__, hw_irq, call_status);
                return;
        }

        /* Have to set XIVE to 0xff to be able to remove a slot */
        call_status = rtas_call(ibm_set_xive, 3, 1, NULL, hw_irq,
                                xics_default_server, 0xff);
        if (call_status != 0) {
                printk(KERN_ERR "%s: ibm_set_xive(0xff) irq=%u returned %d\n",
                        __func__, hw_irq, call_status);
                return;
        }
}

static void ics_rtas_mask_irq(struct irq_data *d)
{
        unsigned int hw_irq = (unsigned int)irqd_to_hwirq(d);

        pr_devel("xics: mask virq %d [hw 0x%x]\n", d->irq, hw_irq);

        if (hw_irq == XICS_IPI || hw_irq == XICS_IRQ_SPURIOUS)
                return;
        ics_rtas_mask_real_irq(hw_irq);
}

static int ics_rtas_set_affinity(struct irq_data *d,
                                 const struct cpumask *cpumask,
                                 bool force)
{
        unsigned int hw_irq = (unsigned int)irqd_to_hwirq(d);
        int status;
        int xics_status[2];
        int irq_server;

        if (hw_irq == XICS_IPI || hw_irq == XICS_IRQ_SPURIOUS)
                return -1;

        status = rtas_call(ibm_get_xive, 1, 3, xics_status, hw_irq);

        if (status) {
                printk(KERN_ERR "%s: ibm,get-xive irq=%u returns %d\n",
                        __func__, hw_irq, status);
                return -1;
        }

        irq_server = xics_get_irq_server(d->irq, cpumask, 1);
        if (irq_server == -1) {
                pr_warn("%s: No online cpus in the mask %*pb for irq %d\n",
                        __func__, cpumask_pr_args(cpumask), d->irq);
                return -1;
        }

        pr_debug("%s: irq %d [hw 0x%x] server: 0x%x\n", __func__, d->irq,
                 hw_irq, irq_server);

        status = rtas_call(ibm_set_xive, 3, 1, NULL,
                           hw_irq, irq_server, xics_status[1]);

        if (status) {
                printk(KERN_ERR "%s: ibm,set-xive irq=%u returns %d\n",
                        __func__, hw_irq, status);
                return -1;
        }

        return IRQ_SET_MASK_OK;
}

static struct irq_chip ics_rtas_irq_chip = {
        .name = "XICS",
        .irq_startup = ics_rtas_startup,
        .irq_mask = ics_rtas_mask_irq,
        .irq_unmask = ics_rtas_unmask_irq,
        .irq_eoi = NULL, /* Patched at init time */
        .irq_set_affinity = ics_rtas_set_affinity,
        .irq_set_type = xics_set_irq_type,
        .irq_retrigger = xics_retrigger,
};

static int ics_rtas_check(struct ics *ics, unsigned int hw_irq)
{
        int status[2];
        int rc;

        if (WARN_ON(hw_irq == XICS_IPI || hw_irq == XICS_IRQ_SPURIOUS))
                return -EINVAL;

        /* Check if RTAS knows about this interrupt */
        rc = rtas_call(ibm_get_xive, 1, 3, status, hw_irq);
        if (rc)
                return -ENXIO;

        return 0;
}

static void ics_rtas_mask_unknown(struct ics *ics, unsigned long vec)
{
        ics_rtas_mask_real_irq(vec);
}

static long ics_rtas_get_server(struct ics *ics, unsigned long vec)
{
        int rc, status[2];

        rc = rtas_call(ibm_get_xive, 1, 3, status, vec);
        if (rc)
                return -1;
        return status[0];
}

static int ics_rtas_host_match(struct ics *ics, struct device_node *node)
{
        /* IBM machines have interrupt parents of various funky types for things
         * like vdevices, events, etc... The trick we use here is to match
         * everything here except the legacy 8259 which is compatible "chrp,iic"
         */
        return !of_device_is_compatible(node, "chrp,iic");
}

/* Only one global & state struct ics */
static struct ics ics_rtas = {
        .check          = ics_rtas_check,
        .mask_unknown   = ics_rtas_mask_unknown,
        .get_server     = ics_rtas_get_server,
        .host_match     = ics_rtas_host_match,
        .chip = &ics_rtas_irq_chip,
};

__init int ics_rtas_init(void)
{
        ibm_get_xive = rtas_function_token(RTAS_FN_IBM_GET_XIVE);
        ibm_set_xive = rtas_function_token(RTAS_FN_IBM_SET_XIVE);
        ibm_int_on  = rtas_function_token(RTAS_FN_IBM_INT_ON);
        ibm_int_off = rtas_function_token(RTAS_FN_IBM_INT_OFF);

        /* We enable the RTAS "ICS" if RTAS is present with the
         * appropriate tokens
         */
        if (ibm_get_xive == RTAS_UNKNOWN_SERVICE ||
            ibm_set_xive == RTAS_UNKNOWN_SERVICE)
                return -ENODEV;

        /* We need to patch our irq chip's EOI to point to the
         * right ICP
         */
        ics_rtas_irq_chip.irq_eoi = icp_ops->eoi;

        /* Register ourselves */
        xics_register_ics(&ics_rtas);

        return 0;
}